The present invention concerns a dual effect compensating tool for fitting hands, particularly for the hands of a clockwork movement. xe2x80x9cDual effectxe2x80x9d means the possibility of controlling the minimum and the maximum driving force of the hands onto their shafts, as will be explained in more detail hereinafter.
FIGS. 1 and 2 show in a way the history of fitting hands on a dial, in particular on the dial of a clockwork movement.
Reference 4 of FIG. 1 shows schematically the oldest manual method. After positioning the hole of a hand above its tool an operator drives it in by means of a rod 41. The proper positioning of a hand, parallel to the dial and along its vertical axis, so that the hands do not catch on each other and do not rub against the dial, thus depends solely on the experience and dexterity of the operator. This method is still used for very small production or for repairs.
FIG. 2 shows an apparatus 5, called a xe2x80x9cBergeonxe2x80x9d bracket, well known in the horological field, comprising a frame 6, provided with a plate 7 for receiving a clockwork movement, said frame 6 supporting a column 8, on which a vertical tool-carrier 9 is mounted, in which three different tools 1, 2 and 3 have been placed, reference 1 corresponding to the tool according to the invention that is described in more detail hereinafter. Each tool includes at one end a detachable stake 37, 27 or 17 adapted to each type of hand, and at the other end a head 38, 28 or 18 on which the driving force will be exerted. Micrometric screws 30, 20, 10 screwed into tool carrier 9 enable the travel of each tool to be adjusted. Tool carrier 9 is pivoted on a tool 8a of column 8 to bring a category of tools 1, 2 or 3 into the axis of plate 7. These tools allow the hour, minute and chronograph hands to be driven in successively in a known manner via stake 17, and minute, hour and small second hand counters via a bent stake, offset with respect to the centre of the movement. These tools are held in the high position by means of springs 12, 22 or 32 arranged between a through hole of micrometric screws 30, 20 or 10 and heads 38, 28 or 18, or subjacent washers 12a or 22a. In the low position, the distance of each stake 17, 27 or 37, screwed into rods or tubes 11, 21 or 32, with respect to plate 7 is adjusted by means of micrometric screws 10, 20 or 30 of frame 5. The head of each tool includes a push-button 18, 28 or 38 on which an operator will exert pressure to drive in a hand.
As will be seen, tool 3 which has just been entirely described, guarantees, with a Bergeon bracket, the verticality of the fitting, whether or not the tool is correctly driven, i.e. neither too tight is properly driven in, i.e. neither too tight nor too loose on its staff, still depends on the skill of the operator, and more precisely his touch sensitivity at the start of driving in the hand. There are, however, three possibilities:
xe2x80x9ctoo greatxe2x80x9d a resistance means that the hand hole is too small and that the hole will have to be squared up before trying to drive the hand in again; increasing the force used to drive it in would risk damaging or offsetting the subjacent gears;
an absence of resistance means that the hand hole is too big and that the latter will have to be discorded; and
xe2x80x9csmallxe2x80x9d resistance means that the hand has been driven in properly.
The tool corresponding to reference 2 allows the first possibility to be checked visually in order not to exceed a predetermined maximum force fixed by bearings. Indeed, tube 21 slides in a tube 25 containing a spring (not visible in FIG. 2) compressed by a piston 24 that can be manoeuvred from the exterior via push-button 28. As can be seen in FIG. 2b is, piston 25 includes perpendicular to its axis a tool 24a which can be moved in an aperture of tube 25 to occupy five different positions, i.e. by compressing the spring to define five maximum force values for example by 500 g stops. In order to carry out the visual check, tube 25 includes close to its base an oblong hole 26, in which a maximum force exceeding indicator 29 can move. In other words, washer 22a has to press against micrometric screw 20 without any movement of indicator 29 being observed during this operation.
A tool of this kind, available for example from Sandoz Fils and Co (La Chaux-de-Fonds, Switzerland) does not however allow the maximum force that must not be exceeded to be precisely adjusted, and especially gives no indication as to the minimum force that has to be reached to drive the hand in properly.
It is thus an object of the present invention to overcome the drawbacks of the prior art by providing a dual effect compensating tool which allows a visual control of both the maximum force and minimum force and which allows the intensity of the force to be precisely adjusted.
Therefore the insert invention concerns a dual effect compensating tool, adaptable to a bracket for fitting hands onto a dial by driving them in. The bracket includes, in the usual manner, a frame connected by a column to a pivoting tool carrier capable of receiving three tools whose height can be adjusted to fit successively the hour, minute and chronograph hands, or hour, minute and small second hand counters. Each tool is characterised in that it includes three parts that flap over each other in a way that can be visually checked. Each tool includes, at its base a stake, adapted to each type of hand, screwed into a lower rod that slides in a tubular part of an intermediate cylindrical element whose other end also slides in a tube at the end of which there is screwed a head on which a force F will be exerted. A first spring, that is determinant for a first force F1, placed in the tubular part of the intermediate element, is compressed between the lower rod into which a first movement indicator is screwed passing through the wall of the intermediate element through an oblong hole, and a first means for adjusting the spring tension formed by a screw and lock-screw device placed inside the intermediate element. Likewise, a second spring, that is determinant for a second force F2, placed in the upper tube, is compressed between the end of the intermediate element, into which a second movement indicator is screwed, passing through an oblong hole of the upper tube, and a second adjustment means, identical to the first and located at the end of the upper tube. These indicators, preferably formed by screws allowing the adjustment means to be dismantled and adjusted, allow, via their movement in the oblong holes, the force F applied to the head to be evaluated with respect to force F1, which is for example the minimum driving force that has to be reached, and with respect to force F2, which is for example the maximum force that must not be exceeded.